Mike Mooney, director of the Center for Underground Tunneling and SmartGeo and Grewcock University Endowed Chair and Professor at Colorado School of Mines, was recently interviewed by USA Today regarding SpaceX founder Elon Musk's goal to build an ultra-high speed underground rail system between New York and Washington, D.C. From the story: Industry leaders said there's room for innovation, particularly if the Tesla and SpaceX CEO can develop a machine that can tunnel through the earth while building retaining walls at the same time — a feat that most tunnel boring machines cannot accomplish ....